The present invention relates to hearing aids. In particular, the present invention pertains to sleeves and exterior housing structures for hearing aids. The invention is intended particularly for use with a hearing aid and hearing aid positioning system and structure such as those disclosed in U.S. Pat. No. 8,605,927, incorporated herein by reference, with the preferred embodiment being adapted for use with a hearing aid positioning system and structure most similar to the third embodiment described in U.S. Pat. No. 8,605,927. That hearing aid has the electronic components within a protective polymer shell which is supportable in a non-occlusive manner within the user's ear canal by the positioning structure.
Hearing aids on the market today are available in different mounting configurations. Many hearing aids include a behind-the-ear (“BTE”) portion which, as the name implies, is mounted behind the user's ear, typically including a sound tube which extends into the user's ear canal to transmit sound from the speaker (called a “receiver” in the hearing aid field, thereby minimizing confusion with a person speaking) contained within the BTE portion. Other hearing aids are considered in-the-ear (“ITE”) hearing aids with some or all of the weight of the hearing aid supported in the conchae bowl of the user's ear. Many hearing aids also include a portion which resides in the user's ear canal, including receiver-in-canal (“RIC”) hearing aids which have only the receiver of the hearing aid in the ear canal, in-the-canal (“ITC”) hearing aids which extend largely into the ear canal but include a portion outside the ear canal, or completely-in-canal (“CIC”) hearing aids which reside entirely in the user's ear canal. Some ITC and CIC hearing aids have used a flexible retrieval line for removing the hearing aid from the ear canal.
In all these hearing aids, trade-offs are made in determining what will be perceived as best sound quality and in weighing sound quality against best comfort of the hearing aid as well as aesthetically. Aesthetically, most users desire a hearing aid which is as inconspicuous as possible, which in turn typically favors placing as much of the hearing aid as deeply in the user's ear canal as possible. Sound quality is somewhat dependent upon proximity of the hearing aid's sound outlet to the eardrum, and placement (depth of canal insertion) affects sound quality more heavily in ITC and CIC hearing aids.
Both sound quality and comfort are also impacted by the degree which the hearing aid “occludes” the ear canal. For some users, minimal occlusion is desired, so ambient sound can reach the user's ear drum through the open space in the ear canal around whichever part of the hearing aid resides in the ear canal. Minimal occlusion helps to avoid any pressure points on the user's ear tissue, and aids in pressure equalization across the ear drum. For other users, significant occlusion is desired. Significant occlusion prevents ambient sound from reaching the user's ear drum, so all (or nearly all) of the sound heard can be modified and amplified through the hearing aid electronics. Significant occlusion also restricts the sound feedback path from the sound outlet back to the hearing aid microphone, particularly important if the microphone inlet is near the sound outlet. Restricting the sound feedback path can allow for higher gains (i.e., more amplification) without the loud and annoying whistles and cracks which can result if sound is repeatedly amplified in a feedback loop.
One part of the difficulty in designing hearing aids is that the anatomical shapes of different users' ears are not uniform. To achieve accurate and consistent placement in the desired location relative to a user's eardrum, many hearing aids use a custom shell which is custom shaped to fit that particular user's shape of ear anatomy. However, customization of the shell involves significant costs which can be avoided with a less customized solution.
For many RIC, ITC and CIC non-custom hearing aids, placement is largely set by the user, i.e., the user pushes the hearing aid (or canal portion) into the ear canal sufficiently far that it comfortably seats in a desired ear canal location by biasing off the wall of the ear canal. A large part of the consistent placement of such RIC, ITC and CIC non-custom hearing aids relies on the gradually decreasing diameter of the ear canal, i.e., the user pushes the hearing aid into the canal until it feels snug but not overly tight. How far the hearing aid is pushed into the ear canal can also result in different amounts of occlusion from user to user and with a single user from one placement to another placement. As more hearing aid solutions become available, proper placement methods for non-custom hearing aids that do not rely on “snugness” in the ear canal are needed.